Multiprotocol Label Switching (MPLS) enables efficient delivery of a wide variety of differentiated, end-to-end services. The Internet Engineering Task Force (IETF) describes architecture for Multiprotocol Label Switching (MPLS) in its Request for Comment (RFC) document denoted as RFC 3031, and entitled “Multiprotocol Label Switching Architecture.”
A fundamental concept in MPLS is that two Label Switching Routers (LSRs) must agree on the meaning of the labels used to forward traffic between and through them. This common understanding is achieved by using a set of procedures, called a label distribution protocol, by which one Label Switch Router (LSR) informs another of label bindings it has made. This document defines a set of such procedures called LDP (for Label Distribution Protocol) by which LSRs distribute labels to support MPLS forwarding along normally routed paths.